1. Field of the Invention
The present disclosure relates to an antenna structure; in particular, to an antenna structure which has two coupled coils and is used in back covers of cell phones.
2. Description of Related Art
With the advancement of wireless communication technology, the user can freely use wireless communication systems to transfer data. Portable electronic devices using wireless communication technology such as notebook computers, cell phones, personal digital assistants (PDA), and smart phones are increasingly widespread and diverse, and the antenna for receiving electromagnetic signals are important components of wireless communication devices.
Radio frequency identification (RFID) is a communication technology using electromagnetic signals to identify specific tags and read and store data. The operating principle of radio frequency identification uses an antenna of an external RFID reader to emit electromagnetic waves to trigger a radio frequency identification tag (such as a non-contact IC card) within a sensing range. The radio frequency identification tag responds to the magnetic field by creating an electric current in the radio frequency identification chip, which in turn emits electromagnetic waves to be read by the reader, thereby achieving the purpose of infrared frequency identification. However, raising sensing range and data transmission quality has always been an important issue for the major manufacturers. Hence, through devoted research combined with application of theory, the present inventor proposes the present disclosure which has a reasonable design and effectively improves upon the above mentioned disadvantages.